Blowback is when a nation's foreign policy leads to attacks against it in the future. More specifically, it's when the foreign policy, originally formulated from a dominant and/or optionally engaging position[1] of realpolitik[2] for or against another sovereign entity and/or its allies, leads to an attack from the same. Some consider it self-evident that things one does today could create problems in the future.

“”By the end of 1993, in Afghanistan itself there were no roads, no schools, just a destroyed country — and the United States was washing its hands of any responsibility. It was in this vacuum that the Taliban and Osama bin Laden would emerge as the dominant players. It is ironic that a man who had almost nothing to do with the victory over the Red Army, Osama bin Laden, would come to personify the power of the jihad.

In the 1980s, the Soviet Union and the United States were engaged in a proxy war in Afghanistan. The CIA had helped the rebel mujaheddin with $3.2-20 billion from the United States through the CIA operation "Cyclone." While many of them were anti-Islamist, there were a few that weren't who pocketed the rest. These payments quite naturally caused Osama bin Laden's movement to grow considerably.

After the war, he organized what he had into Al Qaeda. The organization was involved in many terrorist operations. However, the group truly came to prominence on September 11, 2001, in a series of attacks known as 9/11.